Method of synthesizing large single crystals of quartz



y 1953 l. l. FRIEDMAN ETAL 2,638,408

METHOD OF SYNTHESIZING LARGE SINGLE CRYSTALS OF QUARTZ Filed July 6,1948 3 Sheefls-Sheet 1 mmum HzO-A v \1 v if H20 6'0 s|o ATTORNEY I. l.FRIEDMAN El" AL May 12, 1953 METHOD OF SYNTHESIZING LARGE SINGLECRYSTALS OF QUARTZ Filed July 6, 1948 3 Sheets-Sheet 2 INVENTORS ISlDOREl. FRIEDMAN ORVILLE F. TUTTLE ATTORNEY May 12, 1953 1. l. FRIEDMAN ETALMETHOD OF SYNTHESIZING LARGE SINGLE-CRYSTALS OF QUARTZ Filed July 6,1948 3 Sheets-Sheet 3 INVENTOR5 ISIDORE l. FRIEDMAN ORVILLE F. TUTTLEATTORNEY Patented May 12, 1953 UNITED srArss METHOD OF SYNTHESIZINGLARGE SINGLE; CRYSTALS OF QUARTZ IsidoreI. Friedman, Washington, D. 0.,and V Orville F. Tuttle, Kensington, Md.

Application July 6, 1948, Serial No. 37.176

(Granted under Title 35, U. S. Code (1952).,

see. 266) 2 Claims.

This invention relates to a method of synthesizing lar e Single crystalsof quartz and in particular, to the composition of the solution fromthequartz is crystallized.

The general object of the invention is to provide. asQIutionsaturatedwith respect to quartz atfa given temperature.

It, is also an object of the invention to pro-- vide a solution ofsilica which is of a viscosity sufificientlylow to promote relativelyrapid crystal lizati'on.

These and other objects of the invention will be apparent fromthe-following description and from the drawings hereto appended whichare merely illustrative of physical-chemical relationships found in theapplicants. research or of conventional-apparatus used and are not to betaken as limitative of the method herein desq fihed.

In these drawings,

Figure 1 represents a tri-axial diagram of the ternary system-NazOI-IzO-Si0r at a constant. temperature of 250 C.

Figures. 2. and 3 show the same at temperatures-'of'300 C. and 350 C.respectively.

Figurei shows in section an arrangement of apparatus for carrying theapplicants method into: effect. The showing includes two interconnectedtanks or bombs positioned one of each in. two separate furnaces.

Figure-5 shows in section a single bomb arrangement for carrying theapplicants method intoiefiect.

Referring to Figure 1 the practicable area of quartzconoentration insolution is here shown.

The. area below the lines extending from the H'zotapex; through A, C, Dto the silica apex is the one which is definitive of the applicantsinvention. Here the little circles represent concentrations tested.

very. viscous and crystallization is very slow.

Also concentrations in the vicinity of points 0 and Dare tooviscous forthe same reason. Concentrationsin,theneighborhood of point A, whilerelatively low. in silicaare at thesame time. low

in..,.vi s co sf ity and. the, quartzin .solution. readily In all of thesubdivided areas below the lines aboveindicated quartz is.

, electrical means (not shown).

2. crystallizes out. upon: a, predetermined drop in temperature or upon.evaporation of solution. The. applicantshave found that concentrationsintermediate of these extremes producev maximum. crystallization, for,normal amounts of, agitation.

Figures 2 and 3 show the. relationship of the same three components. attemperatures, of. 300 C. and 350 C. respectively. These increasedtemperatures have, caused the shifting of the. points C, D and E- to.the right, and toward. the SiQz apex, thereby indicatingagreaterconcentration of the S102. Also at these, higher temperatures points Fand A have. shifted towardthe left and toward the H20 apex. Withinthearea of, the diagrams the .various Liquids? indicatedat points A, B, C,D, 'E, andl are concentrations of different sodium. silicatesin water.Thus... it is apparent from. the. diagramsthat whether one makes asolution of, silica with-sodium hydroxide alone. or with a sodiumsilicate, withincertain concentrations, the solidv phase exists asquartz only; that within other concentrations the solid phases bothexistas quartz and-sodium bisilicate in equilibrium with the solution.Also, with the temperatureaincrease shown, the liquids associatedwithzthe. quartz and, the silicatesv changed, in the analogous areas,fromv that shown in the diagram at 250 C. In the operation of themethodthe solutions of the difierent concentrationsof the Liquids, here.described, separated as distinct phases. Their composition wasdetermined by quantitative analysis. In general these liquids werevarious sodium silicates, and the relative proportions present dependedupon the particular concentrationjviz, its position on the diagram.

Figure 4 discloses a conventional arrangement of apparatus for carryingout the applicants method of crystallization. In this figure, IO' andii!- represent two furnaces which are heated by The temperature in thesefurnacesis thermostatically controlled. Saturator tank It andcrystallizing tanlo l3J-contain solution M which may consist of asolution of S102 in from .5 to 20% by. Weight of sodium hydroxide, or asolution of NazO and silica of a concentration. within the definedarea-derived fromany sodium silicate source- Fragments of quartz areshownin the bottom of the saturator tank at I6. Conduits; I8 and. 20connect: tanks ll and l3 as shown. These conduits areprovided withvalves 22 .and 24 by means of which the: rate of circulation of: thesolution is controlled At least ;one: seed crystal 2,8: is suspendedin.,.crysta11izing2tanh. i3 as indicated;

The applicants method of crystallization is not necessarily limited tothe arrangement of apparatus shown by Figure 4. This method may be alsoaccomplished in a single tank or bomb apparatus as illustrated in Figure5. In this figure furnace 50 is shown supporting tank 52 which containsquartz solutions 54 and 56. At least one seed crystal 58 may besuspended as shown. Basket 6! containing quartz fragments 62 may beattached to cover plate 64.

In performing the applicants method by means of a single bomb or tankthe latter is filled with the solution which as above indicated, may besodium hydroxide in water, sodium silicate alone, in water. Cover 64supporting seed crystals 58 and basket 6| containing quartz fragments 62is then placed on the bomb. The furnace may then be heated bythermostatically controlled electrical means (not shown) to atemperature of approximately 375 C. and the solution allowed to reachequilibrium at this temperature. The temperature may then be graduallyreduced to approximately 325 C. The solution of quartz is supersaturatedand the quartz in excess of that which can be dissolved at this lowertemperature crystallizes out on the seed crystals. In this single bomboperation the silica solution at equilibrium separates into two liquidphases shown at 54 and 56 in the drawing. The supernatent phase is oflower density, more aqueous and less silicious than the phase lyingbelow. A seed crystal, suspended so as to extend across the interface ofthese two phases, grows at an uneven rate. The part extending into thelower phase will increase in weight more rapidly as shown at 60 than thepart extending into the supernatant phase. This is due to the differencein silica content of the two phases. The crystal must therefore besuspended so that it will lie entirely within the lower phase.

The method of operation of the apparatus as shown by Figure 4 isbelieved to be obvious from the foregoing description. It consists ofintroducing suflicient solution of the desired concentration viz, .5 to20% of sodium hydroxide in water, or a sodium silicate alone to fillboth tanks. The covers are placed on the tanks and the furnaces may beheated to predetermined temperatures; furnace In to within the range ofabout 250 C. to about 450 C. and furnace I2 to a temperature of fromabout 5 to 50 C. less. After the solution reaches saturation equilibriumin tank ll valves 22 and 24 are opened to permit circulation of thesolution between the tanks. The solution becomes supersaturated in tank[3 and the excess silica crystallizes out as quartz on the seed crystalssuspended in this tank. There is no formation of liquid phases in tanksl l or 13 because of the flow of the solution. The growth of the seedcrystals is therefore uniform and even.

The following specific examples are given in order to illustrate moreclearly the applicants invention EXAlVLPLE 1 A solution of sodiumhydroxide was prepared by diluting 5 cc. of a solution of sodiumhydroxide (containing 782 gms. of NaOH per liter) by the addition theretof 23 cc. of water. The dilute solution contained 3.91 gms. of NaOH. Tothis diluted solution were added 3.3 gms. of ground fused quartz. Thesolution was then placed in a single bomb containing a seed crystal andheated to 360 C. and equilibrated at 350 C. for eight hours. The bomband contained so lution were then cooled at the rate of two degreescentigrade per hour to a temperature of C. and were then quenched undertap water at a temperature of approximately 15 C. The results were asfollows:

Wt. in gms.

before test Seed Crystal after test 0. 0876 gain in weight The seedcrystal started to form faces on some of the corners. Also there weresome separate seeds formed which were approximately 2 mm. in length.

EXAMPLE #2 Results Seed Crystal #2 #3 #5 #10 #26 Weight Before (gms.) 3.290 3.040 5. 450 2. 980 3. 240 Weight After 3. 376 3. 368 5. 536 3. 3833. 470

In this test seeds positioned in the center and lower portion of thebomb gained in weight.

From the foregoing it is apparent that the applicants have developed amethod for the successful crystallization of quartz from silicatesolution. While the description has been drawn to solutions of thealkali metal sodium compounds such as the hydroxide and silicate, it isnot desired to be strictly limited thereto as the hydroxides andsilicates of the other alkali metals such as potassium and lithium maybe used in the same manner. Slight variations in the concentration ofthe solutions used could be made by those skilled in the art to obtainthe equivalent crystallization effect without departing from the spiritor scope of the invention. Such variations are intended to be includedwithin the scope of the invention to the extent as defined by theherewith appended claims.

The invention herein described may be made and used by or for theGovernment of the United States of America for governmental purposeswithout the payment of any royalty thereon or therefor.

What is claimed is:

1. A method of growing larger crystals of quartz by deposition of quartzfrom solution onto crystal seed quartz which comprises cooling in aclosed system in the presence of crystal seed quartz a hot body ofaqueous sodium silicate solution which is in equilibrium saturation withrespect to quart, has a sodium oxide equivalent equal to a concentrationof from about 0.5 to about 20% by weight of sodium hydroxide and is at atemperature within the range of between about 250 and about 450 C., andconducting the cooling of said solution at a rate such that while quartzis deposited therefrom onto the crystal seed quartz, the resultingsolution attains equilibrium saturation with respect to quartz at eachsucceeding lower temperature level.

2. A method of growing larger crystals of quartz by deposition of quartzfrom solution onto crystal seed quartz which comprises cooling to alower temperature within the range of between about 250 and about 350 C.in a closed system in the presence of crystal seed quartz a hot body ofaqueous sodium silicate solution which is in equilibrium saturation withrespect to quartz, has a sodium oxide equivalent equal to aconcentration of from about 0.5 to about 20% by weight of sodiumhydroxide and is at a temperature within the range of between about 325and about 450 0., and conducting the cooling of said solution at a ratesuch that while quartz is deposited therefrom onto the crystal seedquartz, the resulting solution attains equilibrium 6 saturation withrespect to quartz at each succeeding lower temperature level.

ISIDORE I. FRIEDMAN. ORVILLE F. 'I'U'I'ILE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,906,758 Kjellgren May 2, 1933 2,204,180 Gerlach June 11,1940 2,508,208 Wooster May 16, 1950 FOREIGN PATENTS Number Country Date601,552 Great Britain May '1, 1948 OTHER REFERENCES Mellor:Comprehensive Treatise on Inorganic and Theoretical Chemistry, Longmans,Green and Co., London, 1925, vol. 6, page 239.

Kerr et a1.: Recorded Experiments in the Production of Quartz, Bull. ofthe Geological Soc. of Am., vol. 54, April 1943, pages 13 and 14.

1. A METHOD OF GROWING LARGER CRYSTALS OF QUARTZ BY DEPOSITION OF QUARTZFROM SOLUTION ONTO CRYSTAL SEED QUARTZ WHICH COMPRISES COOLING IN ACLOSED SYSTEM IN THE PRESENCE OF CRYSTAL SEED QUARTZ A HOT BODY OFAQUEOUS SODIUM SILICATE SOLUTION WHICH IS IN EQUILIBRIUM SATURATION WITHRESPECT TO QUART, HAS A SODIUM OXIDE EQUIVALENT EQUAL TO A CONCENTRATIONOF FROM ABOUT 0.5 TO ABOUT 20% BY WEIGHT OF SODIUM HYDROXIDE AND IS AT ATEMPERATURE WITHIN THE RANGE OF BETWEEN ABOUT 250 AND ABOUT 450* C., ANDCONDUCTING THE COOLING OF SAID SOLUTION AT A RATE SUCH THAT WHILE QUARTZIS DEPOSITED THEREFROM ONTO THE CRYSTAL SEED QUARTZ, THE RESULTINGSOLUTION ATTAINS EQUILIBRIUM SATURATION WITH RESPECT TO QUARTZ AT EACHSUCCEEDING LOWER TEMPERATURE LEVEL.